The invention relates to an actuator for actuating a valve, with a housing shell made of a magnetically conductive material, a coil support that has an actuation projection and is displaceable within the housing shell while forming an air gap relative thereto, with at least one current-carrying coil wound onto its circumference and with a magnet cylinder enclosed by the coil support while forming an air gap, with a sequence of permanent magnet and pole disk made of a magnetically conductive material arranged axially in the cylinder's interior, wherein the axial width of the coil is greater than the axial length of the pole disk associated with the coil.
An actuator with the described features is disclosed in U.S. Pat. No. 5,345,206. In principle, this actuator can also be used to actuate a valve. The prior-art actuator has a housing, which is closed on one end and is made entirely of a magnetically conductive material. The coil support, which can be driven out of the housing by an actuation projection, is displaceable within the housing. The prior art actuator is distinguished in that the pole disks are narrow compared to the permanent magnets arranged adjacent thereto, and the coils wound onto the coil support are much wider than the associated narrow pole disks.
With this configuration of the prior-art actuator, based on a magnetic saturation of the narrow pole disks, a leakage field from the permanent magnets acting on the coils overlapping the permanent magnets is to be produced deliberately. This configuration accepts the drawback that the magnetic flux provided by the permanent magnet cannot be completely converted into a useful flux to move the coil support, and that the field lines, to a large extent, must overcome a longer path in the air gap next to the pole regions, so that a larger amount of magnetic material is required. To take into account the leakage flux, the coils are dimensioned to overlap by far the width of the associated pole disk. As a result, a relatively large amount of coil material is located on the coil support. This has not only the drawback of increasing the mass of the coil support that must be moved when the actuator is in operation, but the coil is also strongly heated because of the power that is supplied to a coil with a corresponding winding mass. This heating affects the actuator's heat balance and causes the individual coil bodies to expand and consequently to influence the size of the specified air gap and to limit the maximum possible energy density.
These drawbacks have the result that an actuator of the prior art cannot be used to control or actuate valves used in fluid engineering applications. Thus, the object of the invention is to provide an actuator with the initially described features for use in fluid engineering applications. Fluid engineering in this context primarily means the actuation of valves used in hydraulic and compressed air applications.
The means to attain this object, including advantageous embodiments and further developments of the invention, are set forth in the claims, which follow this description.